June 5 (Bloomberg) -- Mexico's Supreme Court took preliminary votes to curb rights broadcasters had gained under a 2006 law, saying it gave the two largest companies, Grupo Televisa SA and TV Azteca SA, unfair advantages.

Automatically letting broadcasters add data and telecommunications services on request violates the constitution's fairness provisions, judges said today during deliberations in Mexico City. The court also decided that auctioning licenses to the highest bidder is unjustified and that 20-year license terms are too long.

The votes are the latest steps by the court to reshape radio and television rules set by the 2006 law. If confirmed in a final decision later, legislators may be forced to redraft the law. Shares of Televisa and TV Azteca fell.

``Why should we prefer colorful better-quality broadcasts at the cost of the monochromatic monopoly of the television companies,'' said Justice Genaro Gongora before today's vote. The session and voting was broadcast live on local television.

The radio and TV law was viewed as beneficial to broadcasters and became known as the ``Televisa law'' after its passage during last year's presidential elections.

`New Law'

``It looks like they are going to strike down enough clauses so as to require Congress to write a new law,'' John Ackerman, a professor with a legal research institute at Mexico's National Autonomous University, said in a telephone interview. ``It's important because the court has had inconsistent criteria on monopoly issues.''

Shares of Televisa, the nation's largest broadcaster, fell 97 centavos, or 1.6 percent, to 60.94 pesos ($5.64) at the close of Mexico trading. TV Azteca, the second-biggest broadcast company, slid the most in 12 weeks, retreating 34 centavos, or 3.2 percent, to 10.44 pesos.

In televised sessions starting last week, the court has rejected several sections of the law, saying they violate Mexico's constitution. Justices decided May 29 that the law gave too much discretion to the Ministry of Communications in awarding licenses.

The vote against license auctions was 9 to 0, with two justices absent due to illness or conflict of interest. The vote against 20-year license terms was 8 to 1, and 9 to 0 against automatic digital services rights. Eight votes are required to strike down a law.

A final vote will be held on all the provisions at issue when discussion of the law concludes.

To contact the reporter on this story: William Freebairn in Mexico City wfreebairn@bloomberg.net.

Last Updated: June 5, 2007 16:29 EDT